This invention relates generally to rocket motor igniters and relates in particular to a molded plastics composite rocket motor pyrogen igniter assembly that may be produced on a production line basis and is readily adaptable for all present day existing and anticipated rocket motors that may be employed by the National Aeronautics and Space Administration for sounding rocket vehicles and in various military rocket motors as well as for anticipated space shuttle payload rocket launches and the like.
In the field of rocket motor ignition where solid propellant grains are utilized, it is the general practice to employ an igniter assembly that includes a pyrogen propellant material and an initiator for the pyrogen with the igniter assembly being, in some instances, formed of a two-piece system wherein the initiator charge is removable from the rocket motor while the pyrogen material is permanently installed and maintained within the combustion chamber adjacent the solid propellant rocket charge. Unitary or single piece non-standard igniter assemblies have been employed but these, as in the two-piece construction, must be individually machined and fabricated for each different rocket motor. This individual machining of the metallic parts employed in constructing the igniter increases the cost of the igniter assembly as well as provides unnecessary weight to the rocket motor. In propelling payloads, such for example in the anticipated space shuttle missions, and in various sounding rockets and other space applications, the additional weight utilized in the igniter serves to reduce the prospective payload weight that could be transported by the solid propellant rocket motor. The firm users identified to date would be the NASA Scout launch vehicle which employs solid rocket motors consisting of Algol III, Castor II-A, Antares, Altair III, and the proposed higher energy versions of each of these which are presently under study; the NASA Delta and Japanese N launch vehicles using solid motors consisting of the Castor II-A, and TE-364; the Air Force Block Five Launch Vehicle, and the Astrobee "F" sounding rocket vehicle. Other potential users include the second stage Minuteman, Terrier Malemute and the Navy HARM missiles. Other potential users of the concept are any of those who may employ solid propellant propulsion systems on space or military rocket motors. The invention also applies to any solid rocket motor design that utilizes a pryogen igniter that is presently known or anticipated.
Most conventional solid rocket motors now employed by NASA and the military utilize non-standard pyrogen igniters having a design that varies from motor to motor and which has changed little over the last 10 to 15 years. The pyrogen performs a common function which is to furnish a controlled, high temperature, high pressue, particle-laden gas to ignite the propellant surface in a solid rocket motor. In reality, the pyrogen igniter of the present invention is itself a miniature solid rocket motor that burns for short duration and consists of very few inert components and a pyrotechnic train. The inert components in presently used igniters of this type consist of numerous parts. The caps or rocket motor case closures are generally fabricated from steel, titanium, or aluminum held in place within the rocket motor casing by a steel snap-ring or machined threads and this cap must be heavily insulated to protect it during rocket motor burning. These known caps or closures contain provisions for initiators and pressure monitoring ports as well as O-ring seals. The pyrogen case or pressure vessel in presently used igniters usually consist of a steel, titanium, aluminum or fiberglass shell that is also heavily insulated inside and out to protect it when the pyrogen and the rocket motor are burning. The insulation material is generally a molded phenolic/asbestos or rubber/asbestos compound. The hot gases exhausted from the pyrogen must pass through one or more nozzles at the end of the shell with the nozzles being generally made from molded phenolic/glass, asbestos or graphite material. A steel or titanium slotted plate or screen is usually included to retain the pyrotechnic ignition pellet charge within the igniter and the inside surface of the pyrogen case insulator generally receives a coating of a rubber liner material to insure good adhesion between the insulator and the solid propellant charge placed in the pyrogen tube.
These non-standard pyrogen igniters have proved sufficient for present day needs; however, they impose unnecessary penalties on the overall systems that use solid propellant rocket motors with pyrogen igniters. These present day pyrogen igniters contain numerous, complex, massive, relatively expensive, heavily insulated metal and non-metal parts that must be fabricated individually and that require many man hours for fabrication and assembly and meticulous inspection throughout for quality control. There is no common or universal design for the various igniters employed by different rocket motor manufacturers and each new design must be evaluated and qualified. Thus, proven reliability suffers because of the relatively few number of devices that are tested and used.
All molded pyrogen igniter designs of the present invention can be incorporated into their respective solid motors during normal operational use and this can be done as part of routine surveillance testing, product improvements, or new procurements or developments.
It is therefore an object of the present invention to provide a novel molded composite rocket motor pyrogen igniter assembly. It is a further object of the present invention to provide a molded composite rocket motor pyrogen igniter assembly that is light in weight and less expensive to construct than presently used igniter assemblies. It is another object of the present invention to provide a novel rocket motor igniter assembly having common geometry and materials that is useful as a standard igniter for numerous solid rocket motors.